1. Field of the Invention
Example embodiments of the present invention relate to a photomask and a method of manufacturing the same, and more particularly, to a binary photomask for defining a photoresist pattern using a transmission-prevention pattern and a method of manufacturing the same.
2. Description of the Related Art
Generally, a mask (e.g., a reticle) is used to form a circuit pattern on a semiconductor substrate. The mask may include an optically transparent quartz substrate and a transmission-prevention pattern (e.g. a chrome pattern) formed on a surface of the quartz substrate. However, if a line width of a circuit pattern in a semiconductor substrate is smaller than a wavelength λ of an exposure light source, it is difficult to form an image on a pupil lens using a first-order light because a diffraction angle of the first-order light passing through the mask may be increased. Even if the image is formed on the pupil lens, contrast may be weak. Therefore, forming a fine pattern, which has a line width smaller than a wavelength of an exposure light source, using a binary mask, which defines a circuit pattern using a transmission-prevention pattern may be difficult.
Conventionally, a phase shift mask using a destructive interference of 0° and 180° may be provided to improve a resolution of a binary mask. A phase shift mask may be classified into an attenuated phase shift mask forming a 180° phase region by using a phase shift material (e.g. MoSiON), and an alternating phase shift mask forming a 180° phase region and a chrome layer by using a trench of the quartz substrate. A chromeless (Cr-less) phase shift mask and a rim-type photomask (a rim mask) are an advanced form of the phase shift mask. A chromeless phase shift mask may form a photoresist pattern by generating a destructive interference on a surface of a 0° phase region (a surface region of the quartz substrate) and a 180° phase region (a trench region). Additionally, the rim mask may complete a photoresist pattern on a semiconductor substrate by forming a chrome pattern on a 0° phase region of the chromeless phase shift mask.
However, phase shift masks as described above may require a plurality of etching processes to form trenches in the quartz substrate and a process to form a chrome pattern in each of the trenches. Therefore, these phase shift masks are generally considered more difficult to manufacture than a binary mask.